TM 10-4930-204-135-30. TANK ASSEMBLY.a. CleaningandInspection.Drycleaning solvent normally has a flash pointof either 100 or 138 degrees F, depending-on thetype being used, but may flash at much lower tem-peratures if contaminated with gasoline or jetfuel. Avoid repeated and prolonged skin contact.Do not use near open flame or excessive heat.(1) The tank must be free of explosive vapors and thorough-ly cleaned before any repairs are attempted; drain the tank of allcontents and open filler plug.Allow filler to remain open for sever-al minutes,If compressed air is available, blow out the tank.Cleanthe tank interior with an approved solvent and dry thoroughly.Precau-tions and procedures outlined in FM10-20 will be applied to the tank.Areas of the tank to be subjected to severe heat must be cleaned tothe bare metal; use a stiff stainless steel wire brush or other suit-able tool for this purpose.Pay particular attention to the seams;heat from a welding torch tends to volatilize tetraethyllead depositscausing toxic fumes.The tank exterior must be cleaned of all dirt,sand, oil, or other foreign matter with a solution of trisodium phos-phate (item 9, App. F), and water; rinse with plain water and dry,Remove paint from any area to be welded.Accumulation of fuel in the tank skids can be ignitedby a welding torch.Before attempting any welding re-pair, be sure the tank skids are equipped with drainholes, and skids are purged and tested for removal offuel(2) Tanks. Drill four 1/2 inch diameter drain holes andfour 1 1/2 inch doameter drain holes in each skid. Refer to figure 5-20for locacion of drilling points. Vapor test the interior of each skidusing MSA Vapor Tester,NSN 6665-00-664-4650, or equivalent. Purge skidby steam cleaning, or other suitable method. Vapor test again and re-purge as required to obtain a safe meter reading. Paint exposed metalaround holes in skids and leave holes open.b. Welding Precautions.(1) Completely drain all fuel from tank to be purged; besure the drained fuel is removed from the area where work will beperformed.(a) Remove all fuel from floor; remove all fuel soakedrags and waste from area.5-46Change 1